The present invention relates to a thermal spray powder. The present invention also relates to a method for forming a thermal spray coating using the thermal spray powder, and a plasma resistant member including a thermal spray coating formed from such thermal spray powder.
In the field of fabricating semiconductor devices or liquid crystal devices, it is common to conduct microfabrication by plasma etching, which is one type of dry etching, using a reactive ion etching apparatus. Therefore, in semiconductor device fabrication apparatuses and liquid crystal device fabrication apparatuses, a member which is exposed during the etching process to the reactive plasma may suffer from erosion (damage). If particles are generated from a member in the semiconductor device fabrication apparatus or liquid crystal device fabrication apparatus by plasma erosion, the particles can deposit on the silicon wafer used in a semiconductor device or the glass substrate used in a liquid crystal device. If the amount of deposited particles is large or if the particles have a large size, the microfabrication cannot be carried out as designed, whereby the device yield decreases and quality defects occur, which can cause the device costs to increase.
In view of this, conventionally plasma erosion of members has been prevented by providing a ceramic thermal spray coating which has plasma erosion resistance on the members which are exposed to reactive plasma during the etching process (see, for example, Japanese Laid-Open Patent Publication No. 2002-80954). However, even a thermal spray coating which has plasma erosion resistance suffers from a certain amount of plasma erosion. If large-sized particles are generated when the thermal spray coating suffers from plasma erosion, this also becomes a factor in decreasing the device yield and quality defects. Therefore, it is desirable to make the size of particles which are generated when a thermal spray coating suffers from plasma erosion to be as small as possible.
In plasma etching, physical etching from ion bombardment of the ionized etching gas is occurring simultaneously with chemical etching from a chemical reaction of the etching gas. Physical etching is a form of anisotropic etching in which the etching rate in the vertical direction with respect to the etching face is higher than the etching rate in the horizontal direction with respect to the etching face. In the case of only conducting physical etching, since the unmasked portions, which need to be etched, and the masked portions, which do not need to be etched, are both etched in the same way by the ion bombardment, the unmasked portions cannot be selectively etched. Accordingly, in microfabrication of semiconductor devices and liquid crystal devices, in which chemical etching capable of selectively etching unmasked portions has to be used in conjunction with physical etching, plasma etching is employed.
Conventionally, in microfabrication by plasma etching, chemical etching has mainly been emphasized. However, in recent years, to cope with increasing miniaturization and decreasing wire width of semiconductor devices and liquid crystal devices, the plasma etching conditions are being changed to achieve higher effects from physical etching. Specifically, etching gases are used in which the ratio of halogen gas such as CF4, CHF3, HBr and HCl, which contribute to chemical etching (selective etching), is reduced, and the ratio of noble gas such as argon or xenon, which contribute to physical etching (anisotropic etching), is increased (for example, see Japanese Laid-Open Patent Publication No. 2001-226773). Thus, there is a need to reexamine the thermal spray coating provided in the semiconductor device fabrication apparatuses and liquid crystal device fabrication apparatuses as a result of this transition in the composition of the etching gas.